Oxygen candles are well-known. Oxygen candles are devices that produce on demand a supply of oxygen by means of a chemical reaction. (The term “chemical reaction” is used herein to exclude electrolytic decomposition and other methods requiring an external source of energy.) An example of an oxygen candle is disclosed in WO 2009/030921 A2 (Molecular Products Group PLC) published 12 Mar. 2009.
A typical oxygen candle comprises a chemical core of an oxygen-containing substance, for example an alkali metal chlorate or perchlorate, in admixture with a catalyst that facilitates lower temperature decomposition of the chemical to oxygen and residual solids. The catalyst may be manganese dioxide or cobalt dioxide, for example, both of which reduce the temperature at which alkali metal chlorates decompose. The chemical core often also comprises a fuel such as iron.
A typical oxygen candle will comprise an ignition apparatus, which is used to trigger the production of oxygen by the device. The ignition apparatus may for example be a spring-loaded shaft with a head coated with a friction-ignitable substance such as phosphorus. When a supply of oxygen is required, the head of the spring-loaded shaft is driven into the surface of the chemical core. When the phosphorus on the head of the spring-loaded shaft is bought into contact with the chemical core, an exothermic reaction is generated. The exothermic reaction initiates the chemical reaction that releases the oxygen the chemical core contains. Alternatively, the ignition apparatus may be an explosive-type ignition, in which a pyrotechnic chemical reaction initiates the release of oxygen from the chemical core.
While the catalyst reduces the temperature at which the chemical reaction can occur, nevertheless the reaction is exothermic, and the exterior of the chemical core typically reaches very high temperatures of the order of 600-1200° C. For this reason the chemical core of the oxygen candle will be surrounded by insulation, and housed within a housing. Considerable efforts have been made to provide portable oxygen candles that can be safely held and used, despite the high temperatures the chemical core reaches when undergoing the chemical reaction.
It is of course desirable to reduce as much as possible the temperature of the oxygen supply provided by an oxygen candle. This is particularly the case with portable oxygen candles that are intended to provide an oxygen supply for medical purposes, in other words directly to a patient, as opposed to devices that are intended to increase the oxygen content in the air in a room, for example. One reason for this is that a medical oxygen supply will be supplied directly to the nose/mouth of the patient via an oxygen tube and face mask, so needs to be at a suitably low temperature, while a supply that is used to increase the air oxygen content will only be released generally into the air so can be at a higher temperature. Another reason is that it is desirable that standard oxygen tubing can be used, as these have a special construction that reduces the risk of them becoming blocked leading to a potential pressure increase and/or the user not receiving any oxygen at the face mask. If standard oxygen tubing can be used, special tubing does not need to be specially manufactured or stored for use with the oxygen candle. To be able to use standard oxygen tubing requires the oxygen to be supplied at a low enough temperature to not melt the standard oxygen tube.
The invention seeks to solve or mitigate some or all of the above-mentioned problems. Alternatively and/or additionally, the invention seeks to provide an improved oxygen generator.